At the time of this post there are 18,084 reviews all-time. So clearly, there weren't 40k posts reviewed in the past few days. There haven't been 40k posts reviewed EVER.

My guess is that SO changed their algorithm for what posts show up in that queue in the first place.

At the time of this post the first review on Sept. 22nd (so over 3 days) is on page 173 (at 50 reviews per page). That means that there have been ~8650 reviews in that time, which is quite a bit less than 40k.